Vehicles, particularly commercial vehicles, such as trucks and buses, typically utilize preventive braking system. Such preventive brake systems typically include an air-operated actuator for applying the brake itself, such as a disc or drum type brake. An example of an air operated actuator is a spring-type brake actuator, wherein the actuator includes a spring, which is compressed by the compressed air, and the compressed spring applies the brake when the compressed air is released for parking or emergency situations.
The spring brake actuator includes a housing (or cylinder), a spring pressure plate (or piston) moveably disposed in the housing, and a diaphragm that is sealingly attached to the housing and the spring pressure plate (or the parking piston). Thus, the diaphragm functions as a seal between the housing and the spring pressure plate. The housing, pressure plate and diaphragm define an air chamber for receiving compressed air. The compressed air inside the air chamber pushes against the spring pressure plate to compress the spring.
Typically, the diaphragm is attached to, and sealed against, the spring pressure plate with a retaining ring, which is mounted on the diaphragm and presses the diaphragm against the pressure plate. The retaining ring must be made with precision. If the ring is too small, it may be difficult to mount the ring on the diaphragm, or the ring may damage the diaphragm. If it is too large, the ring may not press the diaphragm against the pressure plate sufficiently for a secure attachment and seal. As a result, the retaining ring is relatively expensive.